Bed Chop

[Harry Dawg]

Hello Folks.
Hope everyone had a good Monday.
The time has come for me to deal with my rusted out bed. The new fuel tank is on it's way from BJ'S and I need to finish it up.


The tail caps, a fender and one bit of the rear quarter panel need to be replaced. I have half a donor bed that I am planning on using for patch panels. I believe I am going to cut along the body seam to separate the tail caps from the main bed. At first I thought these were spot welded on there, but now I'm not so sure, so I think I'll just chop them off with the angle grinder and weld the new ones on.

Alternatively I was thinking about moving the cut further up into the main bed and going straight across. This way I can just butt weld the two parts together and not have to worry about lining up the tail caps and tail gate barell mounts.

I already burned the fender on there, and it came out pretty alright. If I could do it over I would weld it from the underside, but that's part of learning. I now need a die grinder to remake the body line as best I can where there was a seam.

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[Harry Dawg]

The worst of the rust is in the tail caps.

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[devildog80]

Following

[akguy09]

Best of luck to you. I hate the seams in the bed and I am getting rid of them in my bed as I fixed the rust holes, I filled the seams.

[Harry Dawg]

Best of luck to you. I hate the seams in the bed and I am getting rid of them in my bed as I fixed the rust holes, I filled the seams.

That was my thought as well. Looks to me like an extra place for rust to form, as evidenced by my tail caps.
Would be interested to see some pics of your bed if you got any.

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[tgreese]

The bed seam is two pieces of steel, above and below, bent 90 degrees and spot welded together. The '73-up beds have a space between the inner and outer bed sides behind the seams that holds debris and moisture. The dead space is there so any dents in the inner bed walls won't show through the outside of the bed. Filling the seams from the outside won't stop them from rusting through. My J10 has a series of plastic plugs along the inside bed sides that I presume was used to fill that area between the bed walls with cavity wax. I plan to do that to my J20 at some point ... The single-wall bed should not be as bad in this respect, though it still has the 90-degrees-bent edges of the top and bottom bed sides. Without treating the internal hidden edge of that bed seam, rust will still come from the inside and rust through the outside.

[akguy09]

Good point, since mine were rusty, they got repaired, treated inside and welded together outside before being body worked

[tgreese]

Corrected my [post above to specify that the double wall beds were used '73-up and they are worse in terms of rust.

I guess my main point is that the way the upper and lower panels are joined pretty much guarantees rust along that seam. Even if you weld the seams together from the outside, there will be water and air contacting raw steel through the seam opening on the inside. Not sure how it would have been built otherwise, but the design promotes rust. Any type of a flange between two body panels like that will rust.

I presume it's not as bad for newer cars that dunk the whole body in primer and use plated steel.

[Harry Dawg]

Thanks for your input Tgreese.

Sounds like I am lucky to have the single wall bed... And here I was thinking I had the rustiest J truck on the planet.
This rig will be living under a shed or garage from here on out, so I don't have too much concern on it rusting in the future.
Although the humid climate of Georgia may start to eat away at the seam regardless.
If it does, I reckon I will just fix it again!

Moving forward, would you suggest cutting along the bed seam with an angle grinder and cut off wheel, or try and remove the spot welds with the die grinder? I have a feeling the later will lead to a better job at the end, but I am an apprentice body worker at best and am having a hard time even locating the spot welds.

Thinking if I can just separate the tail caps from the main bed it will leave the 90 degree flange in tact.
This way I have something to weld the new tail caps on to from the back side.

[Glad the Impaler]

For what it's worth - here's my post on bobbing my single wall 8ft bed to a 7ft bed (primarily for offroading benefits).

My bed was in pretty good condition - so the reason for bobbing was not rust related at all.

https://www.fsjnetwork.com/forum/viewto ... 40#p209889

[Harry Dawg]

Hey Glad the Impaler.
Thanks for the info. I have been following your build for some time now, but I didn't realize you had about finished it up!
Looking great by the way. Admirable fab work, and the craftsmanship is outstanding.
I was thinking about bobbing mine, but I just couldn't bring myself to chop the frame.
If departure angle ends up being too much of an issue I might consider this, but for right now I am just going to run a heavy bumper and if I drag so be it.
I do think I might end up with a cleaner bed if I just cut it straight across like you did. Then it will just be one weld versus 3.

[Harry Dawg]

Howdy Y'all.
Hope everyone has been doing well this past week.
It's been hotter than 2 rats fornicating in a wool sock here in GA, so progress has been slow.

I have gotten the rusted tail caps off of the bed, and have some somewhat clean metal to work with.
I tried a variety of methods including; grinding the spot welds with the a die grinder, punching the spot welds out with a spot weld remover drill bit and cutting the spot welds with an angle grinder and cut off wheel.

I found that the best and easiest way to get them off was to use the drill bit. It is quick, quiet and leaves the panel relatively intact.
This does have it's limitations though, as this method only works on easily accesible spot welds that you can get a drill into.

For the inner bed seam, I ended up cutting between the two panels with an angle grinder.
At first I was hitting the spot welds with a die grinder, but being inside the bed wall this just made for a PITA.
Also it would direct the hot sparks and shavings right back at me off the bed wall, and with the heat index being 108 I tired of this very quickly.

Anyways, here are some photos of the current progress. Currently in the process of removing the patch panels from the donor bed.

I also got the fender patch 70% finished. Just need to fill in some pin holes and blend the welded seam a little better.

[Harry Dawg]

Bed pics

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[Harry Dawg]

Tools used

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